"If we look we'll find 'em... the microbes are there. They're these little packages of secrets that are waiting to be opened."

- Anna-Louise Reysenbach

Introduction

Microbes flourish. Inside your gut, in the mucky soil of a marsh, in Antarctic ice, in the hot springs of Yellowstone, in habitats seemingly incompatible with life, microbes flourish.

They were present on Earth 3.5 to 4 billion years ago, and they've been evolving and expanding into new environments ever since. Replicating quickly, exchanging genetic material with each other and with other organisms, bacteria and archaea have become ubiquitous.

Not only are they everywhere, but these tiny organisms also manipulate the environments in which they live. Their presence has driven the development of new ecosystems - some of which allowed for the evolution of more complex organisms. Without microbes, the recycling of essential nutrients on Earth would halt. Microbes communicate; some generate the signals for the formation of metabolically diverse communities. Some use sophisticated signaling to establish complex relationships with higher organisms.

In this unit we will examine examples of the broad diversity of microorganisms and consider their roles in various ecosystems, both natural and man-made. We will also discuss some of the practical applications that derive from the wealth of metabolic diversity that microorganisms possess.